45
Logix
®
520MD+ and 510+ Digital Positioners FCD LGENIM0105-15-AQ – 05/16
flowserve.com
NOTE:
Only those with specific training in PID tuning algorithms
should attempt to adjust the tuning by manually changing the
PID values.
Open Stroke Time is the fastest time it took the valve to stroke from
0% to 100% during Quick-Cal.
Close Stroke Time is the fastest time it took the valve to stroke from
100% to 0% during Quick-Cal.
Minimum Open Time and Minimum Close Time (Speed Limits) are
used to prevent the valve from moving too quickly. This can be used
when the process is sensitive to rapid flow or pressure changes. This
shows the time (in seconds) that the positioner will allow the valve to
travel a full stroke. This speed limit applies to smaller movements of
the valve too.
For example, if the Minimum Open Time were set to 20 seconds, and
the command was changed from 40% to 50%, the positioner would
move the valve at a constant rate, taking 2 seconds to complete the
move. If the Minimum Close Time was set to 0, and the command
was changed from 50% back to 40%, the positioner would make the
move as quickly as possible.
The default values are 0 seconds, meaning the positioner will move
the valve as quickly as possible.
Gain Set with Dual selected, applies independent gains in the open
and closing directions (default). With Single selected, the most con-
servative gains found during calibration are applied in both the open
and closing directions.
10.3.6 Configuration (Characterization)
.
Configuration
.
Characterization
.
MaxFlo Linear
.
MaxFlo Equal %
.
Valdisk Linear
.
Valdisk Equal %
.
ShearStream Linear
.
ShearStream Equal %
.
Custom
The Configuration – Characterization menu allows the user to change
the characterization of the command. This allows a better match
between the input command and the actual fluid flow through the
valve. This feature is typically used with valves that have non-linear
flow characteristics. The positioner makes a correction by applying
an adjustment to the input command according to a characterization
curve. The table below shows the available characterization curve
options. Each point of the Custom curve can be adjusted using the
ValveSight DTM. See Figure 39.
To view the characterization curve options, set the Characterization
switch “Other” before performing a Quick-Cal. Otherwise, the only
option available is “Linear”. If a Quick-Cal is not possible, use the
ValveSight DTM to select the curve.